Generator Type

This isn't a true "solar" question but I thought I'd ask since it appears most of you have backup generators for battery charging.

What type of sine wave does a standard portable generator produce?

I understand the difference between pure and modified, and why each is used. I understand that the newer Honda and Yamaha Dc to AC inverter generators produce a stable pure sine wave. But what about the gas engine-to-direct spinning generators? Do they also produce pure sine wave or is it modified?

What I'm asking is how clean is the wave on a standard portable (non-inverter) generator?

Is the wave the issue with electronics or is it voltage fluctuation?

My understanding is an inverter generator produces clean electrical power close to what is provided by the power company. Good for devices with electronics.

Does a standard generator do the same?

I'm also wondering about whole house standby generators. They are spinning field/armature too, yes? If spinning field/armature does not produce a pure, clean sine wave or non-fluctuating voltage for electronic devices, how to they get sold and installed for whole house use?

I haven't been to one lately but I suspect power station turbines spin a field/armature generator.

Somewhere on here 2manytoys did a scope of some generator output (Yamaha inverter-gen as I recall). It was just as "clean" and well-formed as any you'd get from a utility. Better than some, in fact.

Standard generators produce a true sine wave output, but are more subject to frequency shift from load changes.

I did see that link and read through his tests on the Yamaha unit.

Ok, so the issue on a standard generator is the load causing the frequency to drift off 60 hz? So it's possible a standard generator with a good bit of overhead wattage would not cause a frequency shift?

The actual shape of the output waveform is a function of how it is generated. With inverters (or inverter-generators) this is done electronically by switch the Voltage up and then down in steps. The more steps and the right filtering provides a waveform that is as close to sine as makes no difference (less than 5% distortion).

A standard generator produces the waveform mechanically, by literally passing a magnetic field by the coils: as the field comes closer it becomes more intense and the Voltage goes up, as it moves away the Voltage goes down. At the right RPM this becomes a true 60 Hz (or 50 Hz) sine wave. Changes in engine RPM will cause this to go high or low and vary the Voltage along with it, but as with all things there are tolerances to what constitutes "proper" line Voltage. As long as it stays within those limits it will work.

What I'm asking is how clean is the wave on a standard portable (non-inverter) generator?

Is the wave the issue with electronics or is it voltage fluctuation?

My understanding is an inverter generator produces clean electrical power close to what is provided by the power company. Good for devices with electronics.

Does a standard generator do the same?

I'm also wondering about whole house standby generators. They are spinning field/armature too, yes? If spinning field/armature does not produce a pure, clean sine wave or non-fluctuating voltage for electronic devices, how to they get sold and installed for whole house use?

I haven't been to one lately but I suspect power station turbines spin a field/armature generator.

Hover Dam (and all power plants) use spinnng wires and magnets to produce sine wave, and the cheap generators also produce sine waves. When you overload them, you can distort the waveform, and the frequency wobbles around a bit, but they are good sine waves.

Standard (aka cheap) AC generators (really alternators) have variable output... Some are good, some are not. And depending on your loads, it can dramatically affect the "purity" of the wave form. Inductive and "non-linear" loads (inductions motors, florescent lamps, etc.) all can have some ugly effects on the output wave forms. Many gensets do not have actual "voltage" regulators but use some sort of circuit/feedback to control voltage. That can work fairly well, or really mess up (typically) the crest of the sine waves.

Actually, Bill, a large number of them have only mechanical governors on the engine to maintain RPM (and assume that is the same as maintaining proper V & F). Most of the time this works, unless you near peak capacity or have a sudden change in load. That's the same two things that will mess up the output (momentarily) of inverter-generators.

Yes, the quality and regulation all affect the "overload" point, along with the power factor, but they (rotating alternators) produce a sine wave, not a mod-sine output. The ST head on my listeroid is mostly, pretty good, but I also got a 5KW head, and only extracting 3KW to power the XW6048 charger section.

There is a reason that 60 hrz mechanical gennies run at 900, 1800, or 3600 rpm, as this is a multiple of 60! My 5 kw lister can be made to run at 50hz simpy by slowing it down, and changing the exciter resistor to keep the cottage as desired.

Ok, so how are DC to AC inverters any different than mechanical generators when load is the issue? Wouldn't a change in load affect the the purity of the inverter's output just like the generator?

I'm just trying to understand how one utilizes alternative power with the sensitivity of digital electronics, which are showing up in more consumer appliances. None of use have a mega-watt power station to supply our energy needs. And there is a point where having an unrealiastic excess of reserve wattage is cost prohibitive.

Ok, so how are DC to AC inverters any different than mechanical generators when load is the issue? Wouldn't a change in load affect the the purity of the inverter's output just like the generator?

I'm just trying to understand how one utilizes alternative power with the sensitivity of digital electronics, which are showing up in more consumer appliances. None of use have a mega-watt power station to supply our energy needs. And there is a point where having an unrealiastic excess of reserve wattage is cost prohibitive.

Inverters do not have the mechanical element that generators have. They can react to load changes as near to instantly as makes no difference. Internal combustion engines can not. However, there are sometimes problems caused by having too heavy a load for the battery bank size or wiring quality. In the worst case the Voltage can drop or "appear" to drop enough that the inverter will fault and shut down.

You are quite right about having too big an inverter for the job. No sense spending the extra money or having to feed 20+ Watts just to keep the inverter on when you only need <300 V*A AC.

OU n the real world, the issue is not the quality of the sine we've per se, but rt her the stability of the frequency and the voltge. Cheaper, smaller gennies have a hard time dealing with spike loads ( and unloads!). A 5 kw genny chugging away wi th 1500 wats of load, then throw a 3500 load on it, and the engine will slow down momentarily, dropping the freq, and dropping the voltge. The cheaper, smaller the genny the poorer most gennies will handle such a scenario.

Other cheap gennies don't hold thier speed all that well e en with a steady load. Remember, larger gennies have more rotting mass, which helps even out spikes to some extent.

The "good thing" (from my point of view) with the Inverter/Generators (like Honda, Yamaha and others) is not the frequency stability (for most things, it does not matter that much)--But the ability to throttle back the genset to a lower RPM when lightly loaded...

This can save a significant amount of fuel... For example, most people running an eu2000i (Honda 1,600 watt inverter/generator), probably run at 1/4 load (400 watts) most of the time. The engine will run at a low RPM during this time and consume (somewhat) less fuel (gallons per hour) vs a standard genset that needs to run at 100% RPM to maintain line frequency.

However--at low RPM, the inverter/generators do not have that much excess surge current--sometimes they need to have "eco throttle" turned off to support starting of heavier loads (such as air compressors and A/C units). Of course, if you have "surging" loads to support all the time, then turning ECO Throttle off negates much of the fuel savings.

I see the point everyone is making. I do wonder if RV manufacturers are concerned about the power supplied by mechanical generators. In some instances the generator is the power for all the electrical needs and can be for an extended period. I've seen some with washer/dryers and large screen LCD tv's. I would think that they would be concerned about generator loads affecting the electronic devices.

Most electronic devices have pretty good power supplies in them meant to take the variations in power available. Because they run at far less than line Voltage (and DC instead of AC) what seems like a big change on the input turns into an insignificant blip on the output.

It is a myth, for instance, that computers are ultra-sensitive to power variations. They have great power supplies in them because the circuitry is sensitive, so they filter out and adjust to suit. The average computer can take a 90 VAC MSW input without any trouble at all. Fixed RPM generator? No problem. The same can't be said of things like CRT's or audio equipment which don't necessarily have that good a power supply inside.

Motors like the washing machine or refrigerator are more likely to suffer from (and cause) shifting frequencies and Voltages.

Something told me it couldn't be that bad to run electronics on a generator.

Actually, I lived in Miami in 1992 during Hurricane Andrew. Only electricity for three months was a 4400 watt generator that we ran a few hours in the AM to cool the refrigerator and well pump to get ready for work. In the PM it was ran for several hours until bed for the refrigerator, lights, very limited tv, and the well pump. Never had any issues.

Most electronic devices have pretty good power supplies in them meant to take the variations in power available. Because they run at far less than line Voltage (and DC instead of AC) what seems like a big change on the input turns into an insignificant blip on the output.

It is a myth, for instance, that computers are ultra-sensitive to power variations. They have great power supplies in them because the circuitry is sensitive, so they filter out and adjust to suit. The average computer can take a 90 VAC MSW input without any trouble at all. Fixed RPM generator? No problem. The same can't be said of things like CRT's or audio equipment which don't necessarily have that good a power supply inside.

Motors like the washing machine or refrigerator are more likely to suffer from (and cause) shifting frequencies and Voltages.

+1, I was about to say the same thing. Huge myth that computers can't run well on dirty power inputs! They are designed for large sags and spikes and can even ride out a few milliseconds of a dropout (which is why cheap UPSs work well even though they are offline until an interruption).

We needed portable power inside a rotating chair (medical research), so we grabbed hardware we had in the shop. Worked so well, never upgraded the hardware. Used for a couple of years, no issues.

My previous motorhome had a conventional 5.5KW Onan generator. Ran well, but had an hour gauge, along with a frequency meter. It would drift a little between 58-62 Hz after it was warmed up. Much more drift before that. For the most part, none of the equipment onboard cared (two A/C units, washer/dryer, TVs, satellite receivers, computer, Bose sound system, blah blah). But it ran at a constant speed, sucking down 1.5 gallons per hour.

The Yamaha EF2400iS generator I use produces cleaner power than the grid, and at 1/4 load, sips 1.6 gallons per 8 hours. If I need to replenish the battery bank after a spell of bad weather, I plug an Ioto 75 Amp charger into the generator.

Conventional generator work FINE. The major downside for me is the vast amount of fuel they require vs. an inverter generator, which only runs as fast as the load demands.